The present invention relates to an ultrasound Doppler motion sensor assembly according to the preamble of the main claim. The invention further relates to the use of such a motion sensor device.
Generally known from prior art are ultrasound Doppler motion sensor devices according to the preamble of the main claim. The latter are usually used in an interior space, in particular for purposes of controlling illumination in response to the detected motion, wherein a continuous transmission signal having a typical carrier frequency of approx. 40 kHz radiated (emitted) by the transmitting means is reflected by an object moving in the detection space, the reflected signal is received by the ultrasound reception means, after which mixer and detector means are used to determine a Doppler frequency that depends on a speed of motion of the detection object within the framework of demodulating the reception signal, and evaluate it for the desired motion detection. Filtration usually takes place to make only (e.g., human) motions accessible to detection within a desired frequency window.
Such an ultrasound Doppler technology used for motion sensor purposes has proven itself for numerous years, is suitable for mass production, and has a long service life, so that this technology has become widely disseminated with emphasis on interior spaces, not least because it can be cost-effectively realized via simple and uncritical assembly in conjunction with low component costs. However, this type of known technology also has its problems during everyday operations. For example, the ultrasound transmission signal can only be prevented from being parasitically coupled into the ultrasound reception means with a great technical outlay, in particular given a spatial proximity of the respective ultrasound units in a shared sensor housing. A too strong feedback has a negative impact on a (maximum) motion sensor range, and can even lead to a complete failure of the generic sensor technology.
Another disadvantage to the known technology, in particular when using a plurality of generic ultrasound Doppler motion devices in a shared room or in the area of respective (adjacent) sensors, has to do with undesired influences on the respective adjacent devices, up to and including erroneous detections and erroneous activations. The cause of this problem lies in the fact that, given (usually quartz-controlled) ultrasound oscillators, the signals of adjacently provided or mounted sensor assemblies are so close to each other in the frequency range that a reception part of a first unit can misinterpret a transmission signal of a second unit as a motion detector signal.
Finally, a general problem (and one that also leads to erroneous activations in the present context of motion sensors) is that pressure fluctuations in the ambient air cannot always be avoided, and likewise cause disturbances.